The present invention relates generally to flow control devices, and more particularly, to a self-adjusting fluid flow regulator for use in fluid handling systems which is capable of maintaining a constant flow rate over a wide range of variations in system pressures.
The invention further relates to a fluid flow regulator as mentioned above which is also temperature responsive; i.e., the regulator will adjust the fluid flow rate so as to maintain a given temperature within the environment serviced by the system.
While the principle features of the flow regulator of the present invention are not limited in application to any particular fluid or fluid handling system, its desirable features and its attendant advantages are most apparent when employed in conjunction with air distribution apparatus.
Air distribution systems for automatically controlling the environmental temperature in habitable, enclosed areas generally employ a fan pressurized air source which supplies air through ducts to the various rooms or portions of the enclosure. In each room one or more terminal ports may be found. These terminal ports typically are ceiling mounted, flat type diffusers which direct the discharged air horizontally along the ceiling, causing it to flow towards and down the walls of the enclosure. This flow pattern, in turn, causes the discharged air to mix with and become diluted by the room air. If pressure variations in the duct system cause the flow through the diffusers to become excessively high, objectionable velocity noise may result. On the other hand, if the flow becomes excessively low, the cool air does not move horizontally along the ceiling, but rather drops directly down causing what is known as "cold air dumping." This phenomena may result in objectionable, cold down drafts on the occupants of the room.
It is, therefore, desirable to provide an air distribution apparatus which maintains the air flow between some acceptable maximum and minimum values. It is also desirable that the air distribution apparatus be responsive to changes in the ambient temperature within the enclosure such that, as the temperature rises or falls, the air flow through the system and discharged from the terminal diffusers will be adjusted so as to maintain the temperature within acceptable limits.
Another problem which is encountered in air distribution systems of this type is that the air supply means may be unable to provide a constant pressure air flow to the regulator. Therefore, in order to maintain a constant volume air flow to the terminal port, the air flow regulator must be responsive to air pressure differentials.
Fluid flow regulators, capable of maintaining a constant volume flow rate, have been disclosed in the prior art. For example, U.S. Pat. Nos. 3,037,528 and 3,540,484 disclose constant volume flow regulators as employed in air distribution systems, and U.S. Pat. No. 3,131,716 is directed to a constant flow rate regulator utilized in liquid systems. However, the flow regulators of these prior art patents have disadvantages which are overcome by the present invention. For example, the prior art devices, which employ linear spring systems, are only incrementally adjustable with respect to flow rate, whereas the present invention, which utilizes a non-linear spring system, is infinitely adjustable over a given range of flow rates. Moreover, the present invention is capable of self-adjustment in response to a signal indicative of temperature, whereas the prior art devices make no provision for such adjustment.
Therefore, according to the present invention, there is provided a fluid flow regulator device which is capable of maintaining a substantially constant flow rate to the terminal ports of a fluid distribution system. This device is responsive not only to pressure variations in the distribution system but also to changes in the temperature of the environment which is serviced by the system. Moreover, the present invention contemplates an open loop flow regulation system such that no flow metering element is required downstream from the regulator. Thus, the device is simplified structurally, and the pressure drop which is associated with such metering elements is eliminated. Finally, the flow regulator of the present invention may be utilized within an air distribution system in conjunction with a pneumatic thermostat both of which function with no external energy input other than that derived from the air flow being controlled.